In previous studies of the desalination technology membrane distillation (MD), superhydrophobicity of the membrane has been shown to dramatically decrease fouling in adverse conditions, but the mechanism for this is not well understood. Additionally, air layers present on submerged solid superhydrophobic surfaces have been shown to dramatically reduce biofouling, and air-bubbling has been used to reducing fouling in MD. The present work studies the effect of maintaining air layers on the membrane surface and superhydrophobicity as a new method for preventing fouling of MD membranes by salts, particulates, and organic particles. Superhydrophobic MD membranes were prepared using initiated chemical vapor deposition (iCVD) of perfluorodecyl acrylate (PFDA) on poly(vinyldene fluoride) PVDF membranes and used to study the effects of hydrophobicity on fouling. A static MD setup with evaporation through an MD membrane but no condensing of permeate was used to examine the effect of air exposure on fouling, by measuring the increase in weight of the membrane caused by scale deposition. Theory was derived for the reduction of fouling on superhydrophobic surfaces. Air layers may displace fouling gels, reduce the area of feed in contact with the membrane, reduce foulant adhesion, and enhance superhydrophobicity in a Cassie-Baxter state. The study shows that the presence of air on the membrane surface significantly reduces biological fouling, but in some cases had mildly exacerbating effects on fouling of salts, especially when the air was not saturated with water vapor. Air recharging combined with superhydrophobicity reduced fouling in several cases where hydrophobic membranes alone did little.Keywords: membrane distillation; superhydrophobic surface; air layer; nucleation; anti-fouling

Despite recent advances in clinical procedures, the repair of soft tissue remains a reconstructive challenge. Current technologies such as synthetic implants and dermal flap autografting result in inefficient shape retention and unpredictable aesthetic outcomes. 3D printing, however, can be leveraged to produce superior soft tissue grafts that allow enhanced host integration and volume retention. Here, a novel dual bioink 3D printing strategy is presented that utilizes synthetic and natural materials to create stable, biomimetic soft tissue constructs. A double network ink composed of covalently crosslinked poly(ethylene) glycol and ionically crosslinked alginate acts as a physical support network that promotes cell growth and enables long-tersm graft shape retention. This is coupled with a cell-laden, biodegradable gelatin methacrylate bioink in a hybrid printing technique, and the composite scaffolds are evaluated in their mechanical properties, shape retention, and cytotoxicity. Additionally, a new shape analysis technique utilizing CloudCompare software is developed that expands the available toolbox for assessing scaffold aesthetic properties. With this dynamic 3D bioprinting strategy, complex geometries with robust internal structures can be easily modulated by varying the print ratio of non-degradable to sacrificial strands. The versatility of this hybrid printing fabrication platform can inspire the design of future multi-material regenerative implants.

Breast cancer and its most radical treatment, the mastectomy, significantly impose both physical transformations and emotional pain in thousands of women across the globe. Restoring the natural appearance of a nipple-areola complex directly on the reconstructed breast represents an important psychological healing experience for these women and remains an unresolved clinical challenge, as current restorative techniques render a flattened disfigured skin tab within a single year. To provide a long-term solution for nipple reconstruction, this work presents 3D printed hybrid scaffolds composed of complementary biodegradable gelatin methacrylate and synthetic non-degradable poly(ethylene) glycol hydrogels to foster the regeneration of a viable nipple-areola complex. In vitro results showcased the robust structural capacity and long-term shape retention of the nipple projection amidst internal fibroblastic contraction, while in vivo subcutaneous implantation of the 3D printed nipple-areola demonstrated minimal fibrotic encapsulation, neovascularization, and the formation of healthy granulation tissue. Envisioned as subdermal implants, these nipple-areola bioprinted regenerative grafts have the potential to transform the appearance of the newly reconstructed breast, reduce subsequent surgical intervention, and revolutionize breast reconstruction practices.

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Cardiomyocytes differentiated from human induced pluripotent stem cells (iPSCs) are valuable for the understanding/treatment of the deadly heart diseases and their drug screening. However, the very much needed homogeneous 3D cardiac differentiation of human iPSCs is still challenging. Here, it is discovered surprisingly that Rock inhibitor (RI), used ubiquitously to improve the survival/yield of human iPSCs, induces early gastrulation-like change to human iPSCs in 3D culture and may cause their heterogeneous differentiation into all the three germ layers (i.e., ectoderm, mesoderm, and endoderm) at the commonly used concentration (10 μM). This greatly compromises the capacity of human iPSCs for homogeneous 3D cardiac differentiation. By reducing the RI to 1 μM for 3D culture, the human iPSCs retain high pluripotency/quality in inner cell mass-like solid 3D spheroids. Consequently, the beating efficiency of 3D cardiac differentiation can be improved to more than 95 % in ~7 days (compared to less than ~50 % in 14 days for the 10 μM RI condition). Furthermore, the outset beating time (OBT) of all resultant cardiac spheroids (CSs) is synchronized within only 1 day and they form a synchronously beating 3D construct after 5-day culture in gelatin methacrylol (GelMA) hydrogel, showing high homogeneity (in terms of the OBT) in functional maturity of the CSs. Moreover, the resultant cardiomyocytes are of high quality with key functional ultrastructures and highly responsive to cardiac drugs. These discoveries may greatly facilitate the utilization of human iPSCs for understanding and treating heart diseases.